Item – Theses Canada

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OCLC number
1006673931
Author
Diaz-Quijada, Gerardo Antonio,1965-
Title
Regiochemical analysis of polythiophenes and conformational analysis of oligothiophenes and oligo(thienyl)furans.
Degree
Ph. D. -- Simon Fraser University, 2000
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [2002]
Description
4 microfiches
Notes
Includes bibliographical references.
Abstract
The first regiochemical analysis of self-doped polythiophenes is presented. The regioregularity of sodium poly(3-(3-thienyl)propanesulfonate) and sodium poly(6-(3-thienyl)hexanesulfonate) was determined using one- and two-dimensional nuclear Overhauser effect (NOE), double quantum filtered homonuclear correlational spectroscopy (DQF-COSY), and heteronuclear multiple-quantum coherence (HMQC) experiments. Excellent resolution enhancement of peaks was obtained with a Gaussian multiplication. The configurational dyads and triads were assigned and their relative populations were obtained. The relative ratio of HT to HH dyads in both compounds was determined to be 4:1, based on the areas associated with the aromatic NMR signals. The conformations of oligothiophenes and oligo(thienyl)furans were studied in great detail. Investigation of the torsional behavior of oligothiophenes employing dynamic NMR (DNMR) and rotating frame relaxation measurements indicated that the barriers are too low to be measured by these techniques. The torsional barriers of unsubstituted and alkylsubstituted 2,2'-bithiophene and 2-(2'-thienyl)furan were studied by 'ab initio ' molecular orbital calculations employing a 6-31 G** basis set and including electron correlation in selected compounds. The torsional energy curves were employed in the parameterization of the torsional parameters for the NM force field. The parameterized MM2 force field was used to examine the torsional behavior in hexyl-substituted oligothiophenes and oligo(thienyl)furans with two or three heterocycles. The protocol consisted of (1) performing a series of molecular dynamics simulations for 2-(2'-thienyl)-3-hexylthiophene, 2,5-bis(3'-hexyl-2'-thienyl)thiophene, 2,5-bis(4'-hexyl-2'-thienyl)thiophene, 2,5-bis(3'-hexyl-2'-thienyl)furan and 2,5-bis(4'-hexyl-2'-thienyl)furan, (2) determination of conformationally averaged structures from these simulations and (3) calculation of theoretical NOE build-up curves using a full matrix relaxation treatment. Excellent agreement between the calculated and experimental NOE curves was generally observed, in particular with the 2,2'-bithiophene system.
ISBN
0612616398
9780612616394